Acoustic measuring systems and distance measuring systems are utilized in a variety of applications. For example, acoustic measuring systems are utilized to measure obstacle distance in applications ranging from automotive systems to fossil discovery. Acoustic measuring systems generally operate by first transmitting a pulse of acoustic energy, creating a sound wave. Then a measurement of the time of flight of the sound wave is recorded. The time of flight, which is the time from transmission of the sound wave until a reflection of the sound wave is received, determines the distance of the obstacle. Automotive applications that utilize acoustic measuring systems require reliable detection of the presence of an obstacle. Currently, the reliable detection of obstacles may be opposed by the complex shape of obstacles, as well as environmental and electrical noise causing false obstacle detection.
Acoustic measuring systems often utilize acoustic transducers both to transmit the generated sound wave, and to receive the reflected signal, or echo signal. A standard approach to measuring the distance of an obstacle is to report the time of flight of an object once the echo signal crosses a threshold. However, dependence on the time when an echo signal crosses a threshold is not reliable. Reliability of this method may vary with the fluctuation of the envelope shape of the echo signal. Additionally, as the threshold varies, the time of flight reported for the same obstacle at a same distance will also vary. Accuracy of acoustic measuring systems is important. Errored object detection could be detrimental in automotive and other acoustic measuring applications. Therefore, avoiding skewed object detection related to an error in an object's shape, an object's height, or due to the detection system's threshold configuration is important. Accuracy in time of flight calculations insures proper acoustic measuring system functionality and related reliability.
The use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.